•Locus: the location of a gene inside a chromosome (plural loci )

•Allele:alternative forms of the same gene (i.e.: different eye colours in humans; green and yellow bean seeds).

•A Homozygous indivudual:remembering that information is duplicated with reference to the number of diploid chromosomes, in a homozygous individual you can find identical alleles in both homologous chromosomes.

•A heterozygotic individual: remembering that information is duplicated with reference to the number of diploid chromosomes, in a heterozygous individual has two different alleles of a gene.

•A dominant allele: the present allele in a heterozygous individual

In this example allele A is present, which represents the colour yellow.

•A recessive allele: in a heterozygous individual this allele remains hidden

In this example the allele which represents the colour green is not present

•Genotype: a group of genes present in an individual

•Fenotype: An external manifestation of these genes

In the example the genotype is shown as aa and the fenotype is the green colour of the seed.

•First experiment: he cross-pollinates two purebreeds

P Yelow seeds x Green seeds

F1 100% Yellow seeds

•First experiment analysis:The purebreed traits are repesented by homozygotic individuals for a determined character. The cross breeding produces heterozygous individuals where only the the dominant allele is present (the yellow seed)

P Yellow seeds x Green seeds

AA aa

F1 100% Yellow seeds

Aa

•Second experiment: he crossbreeds the f1 hybrids

f1 Yellow seeds x Yellow seeds

F2 3:1 ratio of yellow to green seeds

•Interpreting the second experiment´s results: the f1 individuals are heterozygous (Aa). We should remember that the new individuals are formed through the union of halpoid gametes during fertilisation and that the gametes come from chromosome separation during myosis. homólogos. The two possible gametes for the two individuals are : A and a

A a

A AA Aa

a Aa aa

f1 Yellow seeds x Yellow seeds

Aa Aa

F2 3 yello seeds for every 1 green

•Third experiment. First part: He crossbreeds two purebreeds which have two different characteristics

P Yellow and smooth x Green and wrinkly

F1 100% yellow and smooth seeds

•Third experiment. Second part: the breeds the f1 seeds with each other

f1 yellow and smooth x yellow and smooth

F2 ratio9:3:3:1

• 9 yellow and smooth.

• 3 yellow and wrinkly.

• 3 green and smooth.

• 1 green and wrinkly.

•Interpreting the third experiment´s results. Part one: the results for part one of the experiment indicate that the yellow alleles (A) are dominant over the green ones (a) and that (L) are dominant over the wrinkly ones (l). The gametes which form the parents (P) are explained by the homólogos chromosome distribution during myosis. This distribution happens randomly. If the seed´s colour and texture locus are in different chromosome pairs, the distribution could happen in the following ways.

P Yellow and smooth x Green and wrinkly (pure parent breeds) AALL aall

F1 100% yellow and smooth seeds

AaLl

AL

al AaLl

•Interpreting the third experiment´s results. Part two: The gametes which form the f1 individuals are again explained by the homologo chromosome distribution during myosis.This distribution happens at random. If the seed´s colour and texture locus are in different chromosome pairs, the distribution could happen in the following ways:

•The AaLl individual may form gametes: AL, Al, aL, al

AL Al aL al

AL AALL AALl AaLL AaLl

Al AALl AAll AaLl Aall

aL AaLL AaLl aaLL aaLl

al AaLl Aall aaLl aall

F2 ratio 9:3:3:1

• 9 yellow and smooth (AALL, AaLL, AaLl, AALl).

• 3 yellow and wrinkly (AAll, Aall)

• 3 green and smooth (aaLL, aaLl)

• 1 green and wrinkly (aall)

f1 Yellow and smooth x Yellow and smooth

AaLl AaLl

Both alleles express the informaton.

Both alleles are visible in the phenotype.

• Genes relative to their blood type contain information for the proteins in red blood cell membranes.

•Our white blood cells recognise those red blood cells with the same proteins as their own.

A blood transfusion in a body with differen proteins can provoke the immune system to react badly and it may even result in the death of the patient.

Phenotype Genotype Can donate blood to

A AA, A0 A, AB

B BB, BO B, AB

AB AB AB

O 00 A, AB, B, O

Genotypes Gametes

AO A y O

BO B y O

AB A y B

AA A

BB B

OO O

•Determined through chromosomes: the XY system (in humans) or XO (in flies: the O represents an absence of chromosomes).

XX XY XO XX

male female

•Karyotype determination: haploid and diploid individuals will develop different genders

•Diploid individual: feeds on honey (it is born infertile).

•The diploid individual feeds on royal gelatine.

•Haploid individual (male)

•Genetic determination: the sex depends on a combination of genes.

•The plantEcbalium elaterium or exploding cucumber is one of the most studied cases. The sex of this plant depends on the genotype of the plant with regards to a series of three alleles.

•Environmental determination: the environmental conditions determine the sex

• The temprature determines a crocodile´s gender. Temperatures of more than 27ºC will result in males.

The presence of an uncommon fragment between chromosomes X and Y determines that those genes whose loci are situated in these fragments will have different inheritance in males and females.

Healthy male Ill male

Healthy female Mujer portadora Ill female

An example of an inherited illness related to gender (the allele which causes the illness is recessive).